The Group IV semiconductor materials enjoy wide acceptance as the materials of choice in a range of devices in numerous markets such as communications, computation, and energy. Currently, particular interest is aimed in the art at improvements in devices utilizing semiconductor thin film technologies due to the widely recognized disadvantages of chemical vapor deposition (CVD) technologies. For example, some of the drawbacks of the current CVD technologies in the fabrication of semiconductor thin films and devices include the slow deposition rates, which limit the cost-effective fabrication of a range of film thicknesses, the difficulty in accommodating large components, high processing temperatures, and the high production of chemical wastes.
In that regard, with the emergence of nanotechnology, there is in general growing interest in leveraging the advantages of these new materials in order to produce low-cost devices with designed functionality using high volume manufacturing on nontraditional substrates. It is therefore desirable to leverage the knowledge of Group IV semiconductor materials and at the same time exploit the advantages of Group IV semiconductor nanoparticles for producing novel thin films which may be readily integrated into a number of devices. Particularly, Group IV nanoparticles in the range of between about 1.0 nm to about 100.0 nm may exhibit a number of unique electronic, magnetic, catalytic, physical, optoelectronic, and optical properties due to quantum confinement and surface energy effects.
With respect to thin films compositions utilizing nanoparticles, U.S. Pat. No. 6,878,871 describes photovoltaic devices having thin layer structures that include inorganic nanostructures, optionally dispersed in a conductive polymer binder. Similarly, U.S. Patent Application Publication No. 2003/0226498 describes semiconductor nanocrystal/conjugated polymer thin films, and U.S. Patent Application Publication No. 2004/0126582 describes materials comprising semiconductor particles embedded in an inorganic or organic matrix. Notably, these references focus on the use of Group II-VI or III-V nanostructures in thin layer structures, rather than thin films formed from Group IV nanostructures.
An account of nanocrystalline silicon particles of about 30 nm in diameter, and formulated in a solvent-binder carrier is given in International Patent Application No. WO2004IB00221. The nanoparticles were mixed with organic binders such as polystyrene in solvents such as chloroform to produce semiconductor inks that were printed on bond paper without further processing. In U.S. Patent Application Publication No. 2006/0154036, composite sintered thin films of Group IV nanoparticles and hydrogenated amorphous Group IV materials are discussed. The Group IV nanoparticles are in the range 0.1 to 10 nm, in which the nanoparticles were passivated, typically using an organic passivation layer. In order to fabricate thin films from these passivated particles, the processing was performed at 400° C., where nanoparticles below 10 nm are used to lower the processing temperature. In both examples, significant amounts of organic materials are present in the Group IV thin film layers, and the composites formed are substantially different than the well-accepted native Group IV semiconductor thin films.
U.S. Pat. No. 5,576,248 describes Group IV semiconductor thin films formed from nanocrystalline silicon and germanium of 1 nm to 100 nm in diameter, where the film thickness is not more than three to four particles deep, yielding film thickness of about 2.5 nm to about 20 nm. For many electronic and photoelectronic applications, Group IV semiconductor thin films of about 200 nm to 3 microns are desirable.
Therefore, there is a need in the art for native Group IV semiconductor thin films of about 200 nm to 3 microns in thickness fabricated from Group IV semiconductor nanoparticles, which thin films are readily made using high volume processing methods.